1. Field of the Invention
The present invention relates to a pixel structure and an organic light emitting device including the pixel structure, and more particularly, the present invention relates to a pixel structure having at least one electronic material layer between an upper electrode and a lower electrode, the pixel structure reducing electrical shorts between the upper and lower electrodes and improving a profile of the electronic material layer, and an organic light emitting device including the pixel structure.
2. Description of the Related Art
Generally, an organic light emitting device, e.g., an Organic Light Emitting Diode (OLED) uses an organic electroluminescence phenomenon in which excitons are formed by recombination of electrons and holes injected respectively through a cathode and an anode in a small molecular or polymer organic thin film. A specific wavelength of light is produced from the energy of the excitations.
Organic light emitting devices include pixel arrays in which a plurality of OLEDs are densely arranged. Each of the OLEDs, which is the smallest unit that emits light, is referred to as a pixel. In a device exhibiting a color image, three pixels emitting red, green and blue light respectively constitute one exhibiting unit. An array of exhibiting units are arranged into a display panel.
An OLED includes an anode, a cathode and an organic light emitting layer arranged between the anode and the cathode. The organic light emitting layer can be classified into several layers according to its function. It can be formed of a multi-layered structure including an Emitting Material Layer (EML), and further including at least one of a Hole Injecting Layer (HIL), a Hole Transporting Layer (HTL), a Hole Blocking Layer (HBL), an Electron Transporting Layer (ETL), and an Electron Injecting Layer (EIL).
This OLED includes an organic light emitting layer formed on a lower electrode corresponding to one of the anode and the cathode using various methods, such as, an inkjet method, dispensing, or photo-to-heat transferring, and an upper electrode corresponding to the other of the anode and the cathode on the organic light emitting layer. An organic light emitting layer needs to cover a lower electrode while keeping a uniform thickness in order to prevent shorts between two electrodes and further to obtain a uniform brightness for multiple pixels.
In forming an organic light emitting layer using dispensing or an ink-jet technique, some solutions have been proposed to satisfy the need for the organic light emitting layer to cover the lower electrode while keeping a uniform thickness. One of the solutions is to adjust the surface energy of upper and side surfaces of banks defining an opening portion to be filled with a fluid organic light emitting layer material on the lower electrode and to adjust the surface energy of an exposed surface of the lower electrode through the opening portion. But, this solution is accompanied with difficult processes for arranging a fine mask exactly and for conducting a surface procedure. Another of the solutions is to provide a tap in a section of the banks. By using this method, it is difficult to optimize a developing and etching condition of the banks.